Aneurysms are local dilatations in blood vessels, in particular arteries that gradually enlarge in time. Unless an aneurysm is adequately treated, it may eventually rupture and cause severe damage to the body, possibly even result in shock or death. Aortic aneurysms are in particular an important cause of death in human adults of 55 years and older.
Traditional repair of an aneurysm entails a major operation with an incision into the aneurysm, evacuation of the clot that is usually contained within, placement of a synthetic graft and wrapping of the graft with the remnants of the artery wall.
A more recent development is the endovascular stent technique. This procedure does not require general anaesthesia and can be done less invasively by simply placing a self-expanding stent via a catheter passed through one of the femoral arteries into the aneurysm to stabilise it. Less fit patients are able to withstand the procedure, hospital stay is cut to 1 to 2 days, and post-operative recovery is shortened considerably.
In WO 95/08289 it is proposed to repair cardiovascular anomalies via the introduction of a photo-activatable biopolymer, which is introduced to the anomaly via a catheter system, after which the polymer is cross-linked. The publication mentions several examples of potentially suitable polymers, wherein it is suggested to be advantageous that the polymers are not only photo-activatable but also biodegradable and resorbable.
A catheter system for delivering fluid materials, such as medicaments to a body vessel is reported in EP 0 667 131 A2. The fluid material is for example a mixture comprising an epoxy resin that cures in the presence of ions.
WO 96/182427 relates to an in situ stent forming catheter for delivering drugs and other fluid materials to an isolated area of a human vessel. As examples of fluid materials, mixtures comprising moisture curing polymeric materials are mentioned, such as cyanoacrylate, polymethylacrylate, polylactic acid and polyglycolic acid.
The American U.S. Pat. No. 6,306,177 describes a method and a related composition for repairing tissue, in particular bone and cartilage. The method involves the use of a curable polyurethane. The publication describes curable polyurethane compositions in general terms and is silent about specific characteristics of a composition for use in (aortic) aneurism repair, such as the viscosity requirements in combination with specific required or desired physical features of the cured compositions, inside the blood vessel.
The Dutch patent 1 005 190 discloses an apparatus for treating a body cavity or body vessel with a curable material, such as polyurethane (PUR). It is described that the apparatus can be used in the treatment of an aorta aneurysm.
Although considerable attention has been paid to the development of delivery systems for fluid material to a body cavity or vessel, it has been found that the availability of compositions for treating cavities or vessels in vivo, in particular for repairing an aneurysm, is highly unsatisfactory.
In particular, it has been found that known polymer compositions suffer from one or more drawbacks, e.g. known compositions have been found to show unsatisfactory handling characteristics, unfavourable curing behaviour, a relatively high level of toxicity, too low biocompatibility, too high thrombogenicity and/or insufficient durability in vivo.